Quitting smoking may do more than protect the lungs and heart — it could also help preserve memory and cognitive function later in life, according to a major long-term study published in American Academy of Neurology journal Neurology.
Researchers who followed more than 32,000 adults in the United States for up to 25 years found that people who quit smoking had a significantly lower risk of developing dementia compared with those who continued smoking. The findings add to growing evidence that smoking affects not only cardiovascular health but also the aging brain.
The study arrives at a time when dementia cases are rising globally and public health experts are increasingly focused on preventable lifestyle factors linked to cognitive decline, including smoking, obesity, physical inactivity, and poor metabolic health.
Scientists analyzed data from the long-running Health and Retirement Study, which tracks Americans aged 50 and older. The analysis included 32,802 adults who did not have dementia at the start of the study period.
Participants were followed between 1995 and 2020, with researchers collecting updated information every two years on smoking habits, body weight, medical history, and lifestyle behaviors. Cognitive performance was evaluated through tests measuring memory, attention, counting backward, and serial subtraction skills.
By the end of the study, nearly 6,000 participants had developed dementia.
Researchers divided participants into three groups: current smokers, former smokers, and people who had never smoked. Individuals who reported smoking during one interview but not the next were classified as having quit smoking during the study.
The results revealed a striking pattern.
Compared with participants who continued smoking, those who quit smoking during the study had a 16% lower risk of dementia. Former smokers and never-smokers also showed lower dementia risk than persistent smokers.
Perhaps more importantly, researchers found that the protective effect appeared to strengthen over time. Dementia risk continued to decline the longer participants remained smoke-free, approaching the risk level of never-smokers after around seven years of smoking cessation.
Lead study author Hui Chen said the findings reinforce the long-term value of quitting smoking for brain health.
“In our study, the benefits appeared stronger with longer time since quitting,” Chen told Medical News Today. “The practical message is: quit smoking, stay physically active, eat well, and manage cardiovascular and metabolic health.”
Researchers also examined one of the most common concerns associated with smoking cessation: weight gain.
The findings suggested that moderate or minimal weight gain after quitting did not erase the cognitive benefits. Participants who gained little or no weight experienced the strongest reduction in dementia risk, while those who gained up to around 11 pounds still showed significantly slower cognitive decline compared with people who continued smoking.
However, the study found that participants who gained more than 22 pounds after quitting smoking did not appear to experience the same cognitive protection.
Even so, experts stressed that concerns about weight gain should not discourage smoking cessation.
“Our study suggests that people who quit, overall, had lower dementia risk and slower cognitive decline than those who continued smoking, so quitting smoking should remain the priority,” Chen said.
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“Some weight gain after quitting is common and should not discourage cessation. However, preventing excessive weight gain may help preserve the long-term brain-health benefits of quitting,” she added.
Health experts not involved in the study said the research highlights the growing understanding that smoking can damage the brain through multiple biological pathways, including vascular injury, chronic inflammation, and oxidative stress.
Dung Trinh, an internist at MemorialCare Medical Group and chief medical officer of the Healthy Brain Clinic, said the findings offer an important public health message.
“What stands out most is that smoking cessation was associated with a reduction in dementia risk, but the benefit was not uniform,” Trinh said.
He noted that people who quit smoking while maintaining healthier weight and metabolic control appeared to preserve the strongest cognitive benefits.
“The practical takeaway is clear: quit smoking, stay quit, and pair cessation with healthy weight and metabolic management,” he said.
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Mental health experts also described the findings as encouraging for smokers worried about long-term cognitive decline.
Anoop Singh, a board-certified psychiatrist from Mindpath Health, said the study sends a hopeful message about the brain’s potential to benefit from lifestyle changes even later in life.
“What stands out most is the hopeful message that quitting smoking may benefit not only the heart and lungs, but also long-term brain health,” Singh said.
He emphasized that quitting smoking should be combined with sustainable lifestyle habits such as physical activity, stress management, proper sleep, balanced nutrition, and behavioral support.
“Some weight gain can happen and should not be seen as failure,” Singh said. “The goal is to combine smoking cessation with steady habits: regular movement, good sleep, stress management, balanced meals, and appropriate medical or behavioral support.”
The findings add to a growing body of evidence linking smoking to cognitive decline and neurodegenerative disease. Researchers increasingly believe that smoking accelerates brain aging by impairing blood flow, increasing oxidative stress, and contributing to inflammation that may damage neurons over time.
With smoking rates in the United States falling below 10% in 2024, according to the American Lung Association, experts say studies like this may further strengthen public health campaigns encouraging smoking cessation not only for cardiovascular and respiratory protection, but also for preserving long-term cognitive health.
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